Comparison of atlas-based auto-segmentation accuracy for radiotherapy in prostate cancer.

Atlas-based auto-segmentation (ABS) procedure used in radiotherapy can be classified into two groups, one using one atlas per patient (sSM) and the other using multiple atlases (sMM). This study evaluated auto-contouring accuracy and contouring time in patients with prostate cancer using the two procedures. The Dice similarity coefficient of sMM was significantly better than that of sSM (prostate [median, 0.81 (range, 0.66-0.91) vs. 0.64 (0.27-0.71), p < 0.01], seminal vesicles [0.49 (0.31-0.80) vs. 0.18 (0.01-0.60), p < 0.05], and rectum [0.81 (0.37-0.91) vs. 0.57 (0.31-0.77), p < 0.01]). The median contouring times were 2.6 (sMM) and 1.3 min (sSM).